Generally, this type of binding processing apparatus is known as an apparatus that performs binding processing on a bunch of sheets supported on a paper mount (sheet support surface) as a post-processing apparatus in an image formation system, or the like. As a binding processing mechanism, known are a mechanism (staple binding mechanism) for binding a bunch of sheets with a staple, and a mechanism (press binding mechanism) for applying narrow pressure to a bunch of sheets with pressurizing surfaces having concavo-convex surfaces to perform press binding.
The press binding mechanism for performing binding processing on a bunch of sheets without using a metal needle is selected as a method of enabling bound sheets to be easily separated and divided and not affecting the environment in discarding documents. On the other hand, such a problem is also known that the sheet peels off when a bunch thickness of a bunch of sheets to perform binding processing is thick, page turning is performed vigorously or the like.
For example, Patent Document 1 discloses a press binding mechanism, and proposes the mechanism for increasing or decreasing a press binding region corresponding to a bunch of sheets to perform binding processing. The Document discloses the mechanism that is a pressurizing mechanism in the shape of gears which rotate in a mutually meshing state in which by adjusting the rotation amount, strong binding is obtained when a band-shaped binding portion is long, and weak binding is obtained when the portion is short.
Further, Patent Document 2 discloses a configuration for enabling a strong binding finish or a weak binding finish to be selected by changing the angle direction of a press binding pressurizing region. In applying narrow pressure to sheets with a pair of pressurizing surfaces to perform press binding, the sheets are deformed in the shape of gathers. Binding easy to peel or binding hard to peel is selected by changing a mesh width (short-side direction) and mesh length (long-side direction) in the arrangement with respect to the sheet turning direction.